REST API documentation

NACHA File Generator API

Generate and validate NACHA ACH files over HTTP. Send JSON describing your batches and entries; get back a file that’s ready for your bank. Free, no API key.

Base URL https://nacha-navigator.com · JSON in, NACHA file out

On this page

Overview
Authentication
Limits
Endpoints
Request format
Errors
Examples
How values are written
NACHA format overview

Overview

The NACHA File Generator API generates compliant NACHA formatted files for ACH transactions. Send a JSON description of the file (a file header, batches and their entries) and get back the file, ready for your bank. The API handles the complexity of NACHA file formatting, including:

Fixed-width field formatting
Batch and file header/footer generation
Control total calculations
Hash sum calculations
Record count tracking
Block padding

Note

NACHA files must adhere to strict formatting rules to be accepted by financial institutions. This API checks your data against those rules before it writes a file, and tells you exactly what to fix when something doesn’t pass.

Endpoints
Endpoint	What it does	Success response
POST /api/v1/nacha/generate	Validates the request and writes the file	The file: text/plain, attachment nacha_file.txt
POST /api/v1/nacha/validate	Runs the same checks without writing a file	JSON: {"message": …, "valid": true}

Prefer a form? The NACHA Generator builds the same files in your browser and exports this exact JSON, so a file you design there can be produced by your systems later. The builder never calls the API: what you type there stays on your device.

Privacy. Requests are processed in memory. Request bodies and generated files are never stored or logged; the only record kept is an anonymous count of files generated, shown on the analytics page.

Authentication

None. The API used to require an API key; keys have been retired and the API is free to use. Clients that still send a key keep working: it is accepted and ignored.

How an old API key is treated
Method	Example	Now
HTTP header	X-API-Key: your_api_key_here	Accepted and ignored
Query parameter	/api/v1/nacha/generate?api_key=your_api_key_here	Accepted and ignored. Avoid it: query strings end up in logs.

The key administration endpoints (GET and POST /admin/api-keys, POST /admin/api-keys/revoke) are retired and answer 404.

Limits

Request limits
Limit	Value	When you exceed it
Rate	About 30 requests a minute per IP address	429 with Retry-After: 60
Body size	1 MB of JSON (several thousand entries)	413
Content type	application/json (charset allowed)	415
Browsers	No CORS headers: call the API from a server or a script, not from a web page on another site	The browser blocks the response

Endpoints

Both endpoints take the same request body and run the same checks, in this order:

The body must be JSON (415 otherwise) and parse (400 otherwise).
Structure: every required key present, no unknown keys, every value a string of the right shape (400 Invalid input data).
NACHA rules: required values filled in, codes from their lists, dates real, numbering and totals that fit their fields (400 NACHA validation failed).
Warnings that don’t block the file, such as a routing number that fails its check digit: reported by /validate.

Generate a NACHA file

POST/api/v1/nacha/generate

Send the request body (see Request format) with Content-Type: application/json. A valid request returns the file itself:

Status 200, Content-Type: text/plain; charset=utf-8, Content-Disposition: attachment; filename=nacha_file.txt, Cache-Control: no-store.
94-character records in uppercase ASCII, each ending with a line feed (LF), the last one included.
Padded with records of nines to a multiple of ten records.

A request that fails a check returns JSON instead. Structure errors are keyed by field, with list positions as strings:

400 · structure error (formatted)

{
  "details": {
    "batches": {
      "0": {
        "entries": {
          "0": {
            "amount": [
              "String does not match expected pattern."
            ]
          }
        }
      }
    },
    "file_header": {
      "immediate_origin": [
        "Missing data for required field."
      ]
    }
  },
  "error": "Invalid input data"
}

Rule errors are a list of messages, each naming its batch, entry and field:

400 · NACHA rule error (formatted)

{
  "details": [
    "Batch 1: Missing required field: company_name"
  ],
  "error": "NACHA validation failed"
}

Validate NACHA data

POST/api/v1/nacha/validate

Checks a request without generating a file. Use it to test data before a payment run. The answer is JSON with a valid flag; errors carry the same details as /generate, with "valid": false and the structure error named Invalid input data structure.

200 · valid

{
  "message": "NACHA data validation successful",
  "valid": true
}

200 · valid, with a warning

{
  "message": "NACHA data validation successful",
  "valid": true,
  "warnings": [
    {
      "code": "aba-check-digit",
      "message": "Batch 1: Entry 1: receiving_dfi_id 021000022 fails the ABA routing number check digit test",
      "path": "batches.0.entries.0.receiving_dfi_id",
      "severity": "warning"
    }
  ]
}

warnings appears only when there is something to report. Each warning has a stable code (listed under Warnings), a severity (warning or info), the field’s path in the request and a message.

Request format

A JSON object with a file_header and at least one batch. Each batch has a batch_header and at least one entry; an entry may carry addenda records.

Every value is a string, amounts and codes included: "amount": "100000" is $1,000.00 (amounts are in cents).
Required keys must be present. Optional keys can be left out: their defaults apply.
Unknown keys are rejected with Unknown field., so a misspelled optional field never goes unnoticed.
Text is printable ASCII: letters, digits, spaces and punctuation. It is written in uppercase.

Request body: the shape

{
  "file_header": {
    "immediate_destination": "123456780",
    "immediate_origin": "1234567890"
  },
  "batches": [
    {
      "batch_header": {
        "service_class_code": "220",
        "company_name": "COMPANY ABC",
        "company_id": "1234567890",
        "standard_entry_class": "PPD",
        "company_entry_description": "PAYROLL",
        "originating_dfi_id": "123456780"
      },
      "entries": [
        {
          "transaction_code": "22",
          "receiving_dfi_id": "021000021",
          "dfi_account_number": "123456789",
          "amount": "100000",
          "individual_name": "JOHN DOE",
          "addenda": [
            { "payment_related_info": "PAY PERIOD 09/01-09/15" }
          ]
        }
      ]
    }
  ]
}

File header

The file header record contains information about the origin and destination of the file.

File header fields
Field	Required	Description	Format and default	Positions
`immediate_destination`Immediate destination	Yes	Routing number of the ACH Operator or receiving point	9 digits, can have a leading space	4–13
`immediate_origin`Immediate origin	Yes	Routing number or other identifier of the originating institution	9 digits, can have a leading space; or a 10-character identifier agreed with your ODFI	14–23
`file_creation_date`File creation date	No	Date the file was created	YYMMDD format (defaults to current date, America/New_York)	24–29
`file_creation_time`File creation time	No	Time the file was created	HHMM format, 24-hour (defaults to current time, America/New_York)	30–33
`file_id_modifier`File ID modifier	No	Distinguishes between multiple files created on same date	A-Z, 0-9 (defaults to 'A')	34
`record_size`Record size	No	Size of each record	094 (default; no other value is valid)	35–37
`blocking_factor`Blocking factor	No	Number of records in a block	10 (default; no other value is valid)	38–39
`format_code`Format code	No	Format code	1 (default)	40
`immediate_destination_name`Immediate destination name	No	Name of the destination institution	Up to 23 characters	41–63
`immediate_origin_name`Immediate origin name	No	Name of the originating institution	Up to 23 characters	64–86
`reference_code`Reference code	No	Reference code for the file	Up to 8 characters	87–94
`priority_code`Priority code	No	Priority of the file	2 digits (defaults to '01', the only value in use)	2–3

Batch header

The batch header contains information about a group of related entries: who sends them, what they are and when they settle. The batch control record that closes each batch is calculated from it and from the entries.

Batch header fields
Field	Required	Description	Format and default	Positions
`service_class_code`Service class code	Yes	Code indicating the type of entries in the batch	200 (mixed debits and credits), 220 (credits only) or 225 (debits only)	2–4
`company_name`Company name	Yes	Name of the company/organization	Up to 16 characters	5–20
`company_discretionary_data`Company discretionary data	No	For discretionary use	Up to 20 characters	21–40
`company_id`Company ID	Yes	Company identification number	Up to 10 characters	41–50
`standard_entry_class`Standard entry class (SEC)	Yes	Code identifying the type of entries	PPD, CCD, CTX, WEB, TEL, ARC, BOC or POP	51–53
`company_entry_description`Company entry description	Yes	Description of the entries	Up to 10 characters	54–63
`company_descriptive_date`Company descriptive date	No	Descriptive date for the company	YYMMDD format (defaults to current date)	64–69
`effective_entry_date`Effective entry date	No	Date the entries should be settled	YYMMDD format (defaults to the next banking day: weekdays except Federal Reserve holidays)	70–75
`settlement_date`Settlement date	No	Settlement date filled by ACH Operator	3 characters (leave it out; defaults to blanks)	76–78
`originator_status_code`Originator status code	No	Code identifying the status of the originator	1 (default) or 2	79
`originating_dfi_id`Originating DFI ID	Yes	Routing number of the originating institution	9 digits (the first 8 are written; the 9th is the check digit)	80–87
`batch_number`Batch number	No	Batch sequence number	Up to 7 digits, ascending through the file (defaults to the previous batch number plus 1, starting at 1)	88–94

Entry detail

Each entry detail record contains information about an individual transaction.

Entry detail fields
Field	Required	Description	Format and default	Positions
`transaction_code`Transaction code	Yes	Code identifying the type of transaction	22 (checking credit), 23 (checking credit prenote), 27 (checking debit), 28 (checking debit prenote), 32 (savings credit), 33 (savings credit prenote), 37 (savings debit) or 38 (savings debit prenote)	2–3
`receiving_dfi_id`Receiving DFI ID	Yes	Routing number of the receiving institution (including check digit)	9 digits (complete routing number)	4–12
`dfi_account_number`Account number	Yes	Account number at the receiving institution	Up to 17 characters	13–29
`amount`Amount (cents)	Yes	Amount of the transaction in cents	Up to 10 digits (e.g., 100000 = $1,000.00); 0 for prenotes	30–39
`individual_id`Individual ID	No	Identification number for the individual	Up to 15 characters (ARC/BOC: the check serial number; POP: check serial number in characters 1-9, terminal city 10-13, terminal state 14-15)	40–54
`individual_name`Individual name	Yes	Name of the individual	Up to 22 characters (CTX: up to 16, written at positions 59-74)	55–76
`discretionary_data`Discretionary data	No	For discretionary use	Up to 2 characters (WEB/TEL debits: the payment type code R, S or ST)	77–78
`trace_number`Trace number	No	Unique identifier for the transaction	Up to 15 digits, unique within the file (defaults to the ODFI routing prefix plus a 7-digit sequence number)	80–94

addenda is an optional array of addenda records (below). Positions are those of the PPD and CCD layouts; CTX, POP and ARC/BOC differences are noted in the formats.

Addenda records

Addenda records contain additional information related to an entry detail record, such as an invoice number. PPD, CCD and WEB entries carry at most one; CTX entries up to 9,999; TEL, ARC, BOC and POP none.

Addenda fields
Field	Required	Description	Format and default	Positions
`addenda_type_code`Addenda type code	No	Type of addenda record	05 (default)	2–3
`payment_related_info`Payment related information	Yes	Additional information about the payment	Up to 80 characters	4–83
`addenda_sequence_number`Addenda sequence number	No	Sequence number for multiple addenda records	Up to 4 digits (defaults to the record's position: 1, 2, 3 and so on)	84–87

Errors

Status codes

Status codes
Status	When	Body
200	Success	generate: the file (text/plain). validate: {"message", "valid": true} plus "warnings" when there are any.
400	The body is not valid JSON	{"error": "Bad request", "message": "Failed to decode JSON object"}
400	The JSON has the wrong shape: a missing, unknown or mistyped field	{"details": {…}, "error": "Invalid input data"} (validate: "Invalid input data structure")
400	The fields break a NACHA rule	{"details": ["…"], "error": "NACHA validation failed"}
404	Unknown path under /api, or a retired /admin/api-keys endpoint	{"error": "Not found", …}
405	Any method other than POST	{"error": "Method not allowed", "message": "The method is not allowed for the requested URL."} with Allow: POST
413	The body is larger than 1 MB	{"error": "Payload too large", "message": "The request body must be 1 MB or less."}
415	Content-Type is not application/json	{"error": "Request must be JSON"}
429	More than about 30 requests a minute from one address	{"error": "Rate limit exceeded"} with Retry-After: 60
500	An unexpected failure on our side (please report it)	{"error": "Internal server error"}

JSON error bodies have their keys in alphabetical order. On /validate, the 400, 415 and 500 bodies also carry "valid": false.

Structure errors

Under details, each field with a problem lists its messages. These are the messages, word for word:

Structure error messages
Message	Cause
Missing data for required field.	A required key is absent.
Unknown field.	A key the API doesn’t know (check the spelling: names are snake_case).
Field may not be null.	A value is null. Leave optional keys out instead.
Not a valid string.	A value is a number or boolean. Every value is a string, amounts included ("100000").
Not a valid list.	"batches", "entries" or "addenda" is not an array.
Invalid input type.	Something that should be an object isn’t (reported under "_schema").
String does not match expected pattern.	A value doesn’t have the required digits, e.g. a routing number that isn’t 9 digits or a date that isn’t YYMMDD.
Longer than maximum length 16.	A value is longer than its field (the number is the limit).
Length must be 1.	A value must have exactly this many characters.
Shorter than minimum length 1.	"batches" or "entries" is empty.
Must be one of: 200, 220, 225.	A code outside its list (service class, SEC code, transaction code…).
Must contain only printable ASCII characters.	Text with accented letters, emoji, tabs or line breaks. Records carry printable ASCII only.
Duplicate trace number found: 123456780000001	Two entries share a trace number (compared as 15 digits, so "1" equals "000000000000001").

NACHA rule errors

Each message is prefixed with where it applies: Batch 1: , Batch 1: Entry 2: or Batch 1: Entry 2, Addenda 1: (counted from 1). <field> stands for the field’s name.

NACHA rule messages
Message	Meaning
Missing required field: <field>	A required value is empty.
<field>: Value must contain only digits	Digits only.
<field>: Date must be in YYMMDD format	Six digits, YYMMDD.
<field>: Time must be in HHMM format	Four digits, HHMM.
<field> must be 2 digits	Exactly this many digits (priority_code, record_size, blocking_factor).
<field> must be at most 23 characters	Longer than the field.
<field> must be at most 7 digits	More digits than the field holds.
<field> must be 9 digits (including check digit)	Routing numbers are all nine digits, including the check digit.
file_id_modifier must be 1 character	One character.
format_code must be '1'	Always 1.
service_class_code must be '200', '220', or '225'	200 mixed, 220 credits only, 225 debits only.
standard_entry_class must be one of: PPD, CCD, CTX, WEB, TEL, ARC, BOC, POP	The SEC codes the API writes.
originator_status_code must be '1' or '2'	1 for almost every originator; 2 for federal government agencies.
transaction_code must be one of: 22, 23, 27, 28, 32, 33, 37, 38	Checking 22/23/27/28, savings 32/33/37/38.
addenda_type_code must be '05' for standard addenda records	Only 05 addenda are written.

Rules added in this version keep the same style. Each closes a gap that let the original API write a file a bank would reject:

Added NACHA rule messages
Message	Meaning
record_size must be '094'	The record size is fixed.
blocking_factor must be '10'	The blocking factor is fixed.
file_id_modifier must be a letter A-Z or a digit 0-9	Lowercase is accepted and written in uppercase.
<field> must be a valid calendar date (YYMMDD)	A date that doesn’t exist, like 260231.
<field> must be a valid time of day (HHMM, 0000-2359)	A time that doesn’t exist, like 2460.
batch_number must be greater than the previous batch's batch number (0000003)	Batch numbers must ascend through the file.
<field> must not be blank	All spaces where a value is required.
<field> must not be blank for PPD entries	The receiver name is required for PPD, CCD, CTX, WEB and TEL entries.
individual_name must be at most 16 characters for CTX entries (Receiving Company Name/ID Number, positions 59-74)	CTX entries hold a shorter name.
individual_id must contain the check serial number for ARC entries	ARC and BOC entries carry the converted check’s serial number.
individual_id must contain the check serial number (characters 1-9), terminal city (10-13) and terminal state (14-15) for POP entries	POP entries pack three values into individual_id.
addenda must contain at most 9999 records	The addenda sequence number has four digits.
batch_number cannot be assigned automatically after batch number 9999999	No room left to number batches automatically.
trace_number cannot be assigned automatically: the 7-digit trace sequence is exhausted	No room left to number entries automatically.
addenda_sequence_number cannot be assigned automatically after 9999	No room left to number addenda automatically.
entry/addenda count 1000000 exceeds the 6-digit Batch Control field (999999)	Too many records in one batch for its control record.
total debit amount exceeds the 12-digit Batch Control field	A batch total beyond $9,999,999,999.99.
batch count 1000000 exceeds the 6-digit File Control field (999999)	Too many batches for the file control record.
entry/addenda count 100000000 exceeds the 8-digit File Control field (99999999)	Too many records for the file control record.
block count 1000000 exceeds the 6-digit File Control field (999999)	Too many blocks for the file control record.
total credit amount exceeds the 12-digit File Control field	A file total beyond $9,999,999,999.99.

Warnings

Warnings never block a file: /generate writes it anyway, and /validate lists them so you can decide.

Warning codes
Code	Severity	Meaning
aba-check-digit	warning	A routing number’s ninth digit doesn’t match the ABA check-digit calculation.
routing-prefix	warning	A routing number doesn’t start with an assigned routing symbol (00–12, 21–32, 61–72, 80).
immediate-destination-format	warning	immediate_destination isn’t a 9-digit routing number.
immediate-origin-format	warning	immediate_origin is neither a routing number nor a 10-character identifier.
priority-code	warning	priority_code isn’t 01, the only value in use.
scc-mismatch	warning	service_class_code 220 (credits only) or 225 (debits only) doesn’t match the batch’s entries.
sec-transaction-code	warning	A credit in a debit-only SEC code (TEL, ARC, BOC, POP).
prenote-amount	warning	A prenote (23, 28, 33, 38) with an amount other than 0.
payment-type-code	warning	A WEB or TEL debit without R, S or ST in discretionary_data.
trace-prefix	warning	A supplied trace number doesn’t start with the ODFI’s first eight digits.
trace-order	warning	Trace numbers don’t ascend within a batch.
addenda-limit	warning	More addenda than the SEC code allows (one for PPD, CCD and WEB; none for TEL, ARC, BOC and POP).
addenda-sequence	warning	Addenda sequence numbers aren’t 0001, 0002, 0003… in order.
effective-date-past	warning	effective_entry_date is before today (Eastern Time).
effective-date-today	info	effective_entry_date is today: it settles today only if your bank gets it before its same-day deadline.
effective-date-non-banking-day	warning	effective_entry_date is a weekend or a Federal Reserve holiday.
company-descriptive-date	warning	company_descriptive_date isn’t a real date.
settlement-date	warning	settlement_date is filled in; the ACH operator sets it.
lowercase	info	Text contains lowercase letters (written in uppercase).

Examples

Copy-ready requests. The routing numbers pass the ABA check digit, so these validate without warnings. Replace them, and every name and account number, with your own.

Basic example

A file with one batch containing one entry: a $1,000.00 payroll credit.

curl https://nacha-navigator.com/api/v1/nacha/generate \
  -H 'Content-Type: application/json' \
  -o nacha_file.txt \
  --data-raw '{
  "file_header": {
    "immediate_destination": "123456780",
    "immediate_origin": "1234567890",
    "immediate_destination_name": "DESTINATION BANK",
    "immediate_origin_name": "ORIGIN COMPANY"
  },
  "batches": [
    {
      "batch_header": {
        "service_class_code": "220",
        "company_name": "COMPANY ABC",
        "company_id": "1234567890",
        "standard_entry_class": "PPD",
        "company_entry_description": "PAYROLL",
        "originating_dfi_id": "123456780"
      },
      "entries": [
        {
          "transaction_code": "22",
          "receiving_dfi_id": "021000021",
          "dfi_account_number": "123456789",
          "amount": "100000",
          "individual_id": "EMP123",
          "individual_name": "JOHN DOE"
        }
      ]
    }
  ]
}'

Response · nacha_file.txt

101 12345678012345678902603021015A094101DESTINATION BANK       ORIGIN COMPANY                 
5220COMPANY ABC                         1234567890PPDPAYROLL   260302260303   1123456780000001
622021000021123456789        0000100000EMP123         JOHN DOE                0123456780000001
822000000100021000020000000000000000001000001234567890                         123456780000001
9000001000001000000010002100002000000000000000000100000                                       
9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999
9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999
9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999
9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999
9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999

Generated for a request sent Monday, March 2, 2026 at 10:15 ET: dates default to the time of your request.

Complex example

Multiple batches and entries, including an addenda record: a payroll batch of two credits, and a corporate batch with one debit.

curl https://nacha-navigator.com/api/v1/nacha/generate \
  -H 'Content-Type: application/json' \
  -o nacha_file.txt \
  --data-raw '{
  "file_header": {
    "immediate_destination": "123456780",
    "immediate_origin": "1234567890",
    "file_id_modifier": "A",
    "immediate_destination_name": "DESTINATION BANK",
    "immediate_origin_name": "ORIGIN COMPANY",
    "reference_code": "SEP2026"
  },
  "batches": [
    {
      "batch_header": {
        "service_class_code": "220",
        "company_name": "COMPANY ABC",
        "company_id": "1234567890",
        "standard_entry_class": "PPD",
        "company_entry_description": "PAYROLL",
        "originating_dfi_id": "123456780"
      },
      "entries": [
        {
          "transaction_code": "22",
          "receiving_dfi_id": "021000021",
          "dfi_account_number": "123456789",
          "amount": "100000",
          "individual_id": "EMP123",
          "individual_name": "JOHN DOE",
          "addenda": [
            {
              "payment_related_info": "EMPLOYEE ID 12345, PAY PERIOD 09/01/2026-09/15/2026"
            }
          ]
        },
        {
          "transaction_code": "32",
          "receiving_dfi_id": "011000138",
          "dfi_account_number": "987654321",
          "amount": "150000",
          "individual_id": "EMP456",
          "individual_name": "JANE SMITH"
        }
      ]
    },
    {
      "batch_header": {
        "service_class_code": "225",
        "company_name": "COMPANY ABC",
        "company_id": "1234567890",
        "standard_entry_class": "CCD",
        "company_entry_description": "INVOICE",
        "originating_dfi_id": "123456780"
      },
      "entries": [
        {
          "transaction_code": "27",
          "receiving_dfi_id": "121000248",
          "dfi_account_number": "543210987",
          "amount": "250000",
          "individual_id": "INV-7731",
          "individual_name": "ACME SUPPLIES"
        }
      ]
    }
  ]
}'

Response · nacha_file.txt

101 12345678012345678902603021015A094101DESTINATION BANK       ORIGIN COMPANY         SEP2026 
5220COMPANY ABC                         1234567890PPDPAYROLL   260302260303   1123456780000001
622021000021123456789        0000100000EMP123         JOHN DOE                1123456780000001
705EMPLOYEE ID 12345, PAY PERIOD 09/01/2026-09/15/2026                             00010000001
632011000138987654321        0000150000EMP456         JANE SMITH              0123456780000002
822000000300032000150000000000000000002500001234567890                         123456780000001
5225COMPANY ABC                         1234567890CCDINVOICE   260302260303   1123456780000002
627121000248543210987        0000250000INV-7731       ACME SUPPLIES           0123456780000003
822500000100121000240000002500000000000000001234567890                         123456780000002
9000002000001000000040015300039000000250000000000250000

Generated for a request sent Monday, March 2, 2026 at 10:15 ET: dates default to the time of your request.

The raw request

HTTP

POST /api/v1/nacha/generate HTTP/1.1
Host: nacha-navigator.com
Content-Type: application/json

{
  "file_header": {
    "immediate_destination": "123456780",
    "immediate_origin": "1234567890",
    "immediate_destination_name": "DESTINATION BANK",
    "immediate_origin_name": "ORIGIN COMPANY"
  },
  "batches": [
    {
      "batch_header": {
        "service_class_code": "220",
        "company_name": "COMPANY ABC",
        "company_id": "1234567890",
        "standard_entry_class": "PPD",
        "company_entry_description": "PAYROLL",
        "originating_dfi_id": "123456780"
      },
      "entries": [
        {
          "transaction_code": "22",
          "receiving_dfi_id": "021000021",
          "dfi_account_number": "123456789",
          "amount": "100000",
          "individual_id": "EMP123",
          "individual_name": "JOHN DOE"
        }
      ]
    }
  ]
}

Using Postman

Create a request and set the method to POST.
Enter the URL https://nacha-navigator.com/api/v1/nacha/generate.
Under Headers, add Content-Type: application/json. No API key is needed.
Under Body, choose raw and JSON, and paste one of the examples.
Click Send. The response is the file; use Save response → Save to a file to keep it.

How values are written

Defaults and automatic values
Field	When you leave it out
file_creation_date, file_creation_time	The date and time of the request, Eastern Time (America/New_York).
effective_entry_date	The next banking day after today: weekdays except Federal Reserve holidays.
company_descriptive_date	Today.
batch_number	The previous batch’s number plus 1, starting at 1. Numbers you supply must ascend.
trace_number	The ODFI’s first eight digits plus a seven-digit sequence, unique in the file, skipping numbers you supplied.
addenda_sequence_number	1, 2, 3… for each entry’s addenda records.
priority_code, file_id_modifier, record_size, blocking_factor, format_code	01, A, 094, 10 and 1.
originator_status_code, settlement_date, addenda_type_code	1, three blanks (the ACH operator fills it in) and 05.

Uppercase. Lowercase letters are written in uppercase. Accented letters are rejected rather than guessed at: convert “José” to “JOSE” before you send it.
Immediate destination and origin. A 9-digit routing number is written with its leading blank (" 123456780"); a 10-character value, such as a company identifier, is written as given.
Service class code is required: 200 for mixed debits and credits, 220 credits only, 225 debits only. A mismatch with the entries is a warning.
Prenotes (transaction codes 23, 28, 33 and 38) carry an amount of 0.
SEC-specific layouts are written for you: CTX entries get the addenda count and a 16-character name; ARC and BOC take the check serial number in individual_id; POP packs the serial number (9), terminal city (4) and state (2) into it; WEB and TEL debits carry the payment type (R, S or ST) in discretionary_data.

Changes from the original API

The request format and responses are unchanged. These fixes change the files it writes:

The batch control record’s ODFI and batch number are at positions 80–94, where the specification puts them, and the batch number matches its batch header.
Entry/addenda counts and the block count include addenda records.
Files are padded to an exact multiple of ten records, matching the block count.
A 10-character immediate destination or origin no longer shifts the rest of the file header.
Missing trace numbers are assigned instead of written as zeros; addenda sequence numbers and batch numbers count up.
Default dates come from the time of each request, not from when the server started.
Line breaks and non-ASCII text are rejected, and totals or counts too large for their field are errors instead of being cut off.
Malformed JSON is a 400 (was 500); unknown paths and wrong methods answer in JSON.

NACHA format overview

A NACHA file is plain text. Each record is exactly 94 characters long, and its first character says what kind of record it is:

File Header (1): the destination, the origin and when the file was created.
Batch Header (5): the company, the SEC code and the effective date of a group of entries.
Entry Detail (6): one payment: routing and account number, amount and receiver.
Addenda (7): optional extra information for an entry; CTX entries can have many.
Batch Control (8): counts, totals and the entry hash of the batch. Generated for you.
File Control (9): the same totals for the whole file. Generated for you.

Files are written in blocks of ten records; the last block is filled with records of nines. The NACHA file format reference describes every field of every record.

Important

NACHA files are typically validated by the receiving financial institution. Ensure that your data is accurate and follows the NACHA specifications, and test with your bank before you send live payments.

Build a file in your browser Check a file in the NACHA Viewer File format reference